THIS STUDY seeks a quantitative evaluation of the energy consumed by Na + -K + transport in the brain. Particular reference is attached to the Na + -K + leak fluxes and associated active transport which occur in the EEG-arrested brain. Synaptic transmission was blocked by pentobarbital to obtain a flat EEG. The effects of lidocaine and of ouabain on cerebral oxygen and glucose consumption were then measured using the sagittal sinus outflow technique' 1 * in dogs on cardiopulmonary bypass circulation. In line with previous studies'14 it was assumed that lidocaine restricts Na + -K + leak fluxes by blocking membrane permeability, and, by this effect, reducing the demand for Na + -K + transport. The remaining Na + -K + transport was blocked by ouabain, 8 a specific Na + -K + sensitive ATPase inhibitor. Ouabain was injected into the systemic circulation but crossed the blood-brain barrier and caused ion transport inhibition. This effect was shown by measurements of the extracellular K + concentration in the cerebral cortex by potassium electrodes. MethodsTwelve mongrel dogs weighing 23-38 kg were anesthetized by thiopental 17-27 mg/kg (mean 20.8 mg/kg) intravenously. Endotracheal intubation was performed after muscular relaxation using gallamine 2-8 mg/kg. Respiration was controlled by mechanical ventilation. Anesthesia was maintained with halothane 1-1.5% mixed in 25/75% oxygen/air. During cardiopulmonary bypass circulation this gas mixture was led through the bubble-oxygenator. The femoral vessels on the right side were cannulated for BP and central venous pressure measurements. Blood gases, acid-base status, and hemoglobin concentration were repeatedly measured. Blood gases and acid-base status were measured at 37°C and corrected for animal temperature. Metabolic acidosis was corrected with bicarbonate, according to the formula: base excess (BE) X body weight (kg) X 0.3. Ventilation, or alternatively gas flow, through the bubble-oxygenator was adjusted to ensure normocapnia or slight hypocapnia.The heart was exposed through a right thoracotomy. The left femoral artery was cannulated using a metal cannula. A multiperforated cannula was inserted in the right atrium allowing drainage of the venous blood to a Rygg-Kyvsgaard bubbleoxygenator (Venoterm 5000) primed with Haemaccel (Haemaccel is a collodial plasma substitute, 1 ml containing 35 mg polygetin, 8.5 mg NaCl, 0.38 mg KC1, 0.7 mg CaCl,) 1000 ml and Ringer's solution 300 ml to obtain hemodilution. The oxygenated blood was pumped by roller-pump into the animal via the cannula in the left femoral artery. Heparinization was induced by heparin 3 mg/kg and maintained by 1 mg/kg/h. Cardioplegia was obtained by flushing the coronary circulation using potassium chloride 1 M after clamping the ascending aorta.Cardiopulmonary bypass circulation was maintained at a flow rate of 100 ml/kg/min. BP was controlled within 50-100 mm Hg by occasional injection of methoxamine 0.5-1 mg or chlorpromazine 1-2 mg. Brain temperature was maintained at 37°C by adjusting the water temper...

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Cerebral blood flow and metabolism were measured repeatedly during surgery for cerebral tumours by a modification of the classical Kety & Schmidt method using 133Xe infusion intravenously. Our standard procedure for neuroanaesthesia (pentobarbitone-fentanyl induction, halothane-nitrous oxide maintenance) reduced blood flow from 47.1 to 24.2 ml X 100 g X ml-1 and metabolism from 3.30 to 1.83 ml O2 X 100 g-1 X ml-1. PaCO2 was reduced by hyperventilation from 5.3 to 3.6 kPa. Additional thiopental loading and maintenance using 4 + 4 mg X kg-1 (n = 5) or 8 + 8 mg X kg-1 (n = 5) reduced cerebral metabolism by an additional 15% (P less than 0.01) and blood flow by 16.5% (P less than 0.01), while mean arterial blood pressure fell from 11.0 to 9.9 kPa (P less than 0.05). PaCO2 remained unchanged. This additional reduction in cerebral metabolism and blood flow is small, but we nevertheless conclude that it may well be of clinical interest to the problem of protecting the brain in case of episodes of focal cerebral ischaemia which may arise peroperatively during intracranial surgery.

»At blive behandlet ordentligt – eller bare blive behandlet« Psyke og Logos, 2001, 22, 695-716